1. Field of the Invention
The present invention relates to mechanical clutches, in general and, more particularly, to one-way, bi-directional clutches.
2. Background Information
One-way, bi-directional clutch devices are mechanical devices that transmit torque from an input shaft to an output shaft in either rotational direction, but do not transmit torque from the output shaft to the input shaft. One-way, bi-directional clutches typically include a brake assembly that engages when more torque is applied to the output shaft than the amount of torque applied to the input shaft. The brake assembly, when engaged, prevents torque from translating from the output shaft to the input shaft in both directions.
One-way, bi-directional clutches, also commonly known as “no-back clutches,” are used in numerous applications. No-back clutches are utilized where a user desires 1) to selectively control the movement of a mechanical device using a power source, and 2) to prevent undesirable movement of the mechanical device due to outside forces acting on the device. For example, no-back clutches are used to control the flaps on airplane wings, where a pilot may desire to raise or lower the wing flap, but does not desire to have the wing flap raise or lower under the force of the wind travelling over the wing. No back clutches are also commonly found on conveyor belts that operate at an angle in order to ensure that the conveyor belt, and its payload, do not reverse direction unless intended. There are at least three (3) known types of no-back clutches: the wrap spring-type, the sprag-type, and the locking wedge-type. Each of the above-listed types of no-back clutches, however, has various shortcomings.
For example, the wrap spring-type is unable to accommodate relatively large loads and/or shock loading. Therefore, the wrap spring-type design often requires a second locking device to ensure the clutch will lock, as desired under all loads.
The sprag-type no-back clutch consists of two standard one-way sprag clutches placed in series with a driving mechanism between them. The driving mechanism unlocks the one-way sprag clutches when driven from one side. However, the sprags of the sprag-type clutch are often forced back and forth between to an unlocked and locked position when the operator attempts to drive the input shaft in the same directions as the load on the output shaft. Such action often results in undesirable chatter or ratcheting.
The locking wedge-type typically includes a center locking bar having sharp edges at both ends (i.e., 2 points of contact). Because only two points of contact are used to prevent torque from translating torque from the output shaft to the input shaft, the locking wedge-type clutch suffers from a short field life due to failures.
Therefore, it is desirable to provide a one-way, bi-directional clutch that overcomes the known shortcomings in the art.